Rage

What is the maximum valve spring load (pounds) at max cam lift for which a stock Merc 496HO hydraulic roller lifter is capable of working properly ie not allowing excessive valve train clearance (valve train clearance noise) do to the hydraulic lifter 's internal piston compressing or bottoming out in the lifter body during engine operation?

FYI current set up is 150# closed valve seat load and 410# max load at 0.596 " max lift.

Rage

ttt

FIXX

iTrader: (2)

FYI-----http://www.jegs.com/p/Comp-Cams/Comp-Cams-High-Energy-Hydraulic-Roller-Lifters/755074/10002/-1


again,your lifter is the same lifter as for a 454-502 gen6..comp cams reccomends you changing your lifters for anything over .570 for oiling issues and another reason.look at the jeggs pic supplyed,go to 454/502--8.1 vortech and look at the lifter..your lifter in your 496 look the same as the gen 6 lifters which requires a dog bone per intake and exhaust lifter, they also require a spring steel retainer that holds all the dog bones in place..look at the pic from jeggs,you can see on the top side of the lifter,their a flat spot machined on each side of the lifter that the dog bone fits over to keep the lifter from spinning or turning..When you go over the max .570 lift limit the lifter lifts the dog bones off the block and the lifters go beyond their machines serfaces and causes the lifter to hang up on the dog bone which is probably the chatter noise your hearing,the dog bones slapping on top of the lifter bores when they seat.

your spring pressures should be ok for your lift ide prefer a little lower ,it also depends on what style valve springs your using..after installing your cam does your boat seem to be hitting a wall? no matter what your do,differant props seems to have the same power no matter what you do?

then replace the lifters with the retro fit roller lifters and your problems will go away..also look at your lifter,the 570 max rule applys when the lifters side oil hole is in a higher position,then you have ,more then a .570 lift the hole in the side of the lifter and the lifers gruve goes beyond the oil hole in the lifter bores and starves the lifter for oil and wont pump up..

p.s you may need to replace the push rods to!

Rage

Mrfixall

The engine valve train has been quiet for ~200 hours with the same set up (with the "dog bones" as you described) but now after I broke a rocker stud and replaced all the Crane studs with the same size ARP studs I am getting some valve train noise. The Valve train is mostly HP3 race engine components and geometry IE, cam, Crane Blue Racer roller rockers, Trend push rods, bronze valve guides, Ferrea valves, vitron seals, Crane studs(now replaced with ARP), polylocks. The springs are Comp Cam 929's instead of the Nascar Springs and the lifters stock GM instead of the Cranes. I checked component condition and function for the cylinder where the stud broke and everything was fine (push rod not bent, spring not broken, lifter slides freely in bore (gravity) and the piston will compress and recover back to the piston stop, rocker undamaged, oil pressure at idle 50 - 60 psi).

The new Comp Cam lifter for the 496 according to Comp Cam tech support is: steel body, Comp Cam design/specification, made in the USA by any one or all of 3-4 vendors. The bad news is that it is only recommended for max spring loads of 300-330 pounds and my max load is 410 pounds. At higher than the rated spring load the CC lifters will allegidly bleed down and valve train noise is likely as well as accellerated lifter wearout per Comp Cam.

I have not run the engine hard (only idle speed) after the stud replacement since I did not like the sound of it so do not know if performance has changed. It ran fine before up to 5800 rpm.